Spectrometers are well-known in the art of analytical instruments. For many years they have been used as detector systems, concentration measurers and combinations of both. Over the years sophisticated and highly-sensitive instruments have become the norm, especially in laboratory environments, but because of desire to perform more field analyses, portable units have been developed. Because of their size and portability, most of these units are not suitable for the high-caliber studies that the lab versions are capable of performing, thus making a need for high-quality and reliable portable systems paramount in the field. In addition, there is also a desire for less bulky but highly accurate instruments for laboratory use. Plus, it is desired that the instrument be adaptable for a wide variety of analyses, and not just limited to certain types of compounds or analytes.
Absorption spectroscopy is based on the principle of colorimetry, which involves the determination of a substance from its ability to absorb light. Light is passed through the test sample (which is a solution or a transparent substance) and the amount of light absorbed by the sample is recorded. The wavelength at which the absorbance took place is also recorded. This absorption spectrum not only provides quantitative data on the light absorbance characteristics of the sample, but can also serve as a “fingerprint” for qualitatively identifying the absorbing substance.
Spectrometric measurements of light are performed in basically two ways, dispersion-based techniques and filter-based techniques. In the dispersion-based approach, a radiation dispersion device such as a prism or diffraction grating is used to separate the incident polychromatic light into its spectral contents. The spectrally separated light is then projected onto a photo detector to measure the relative intensity in each spectral range.
The present invention provides a spectrometer that is easily adapted for analysis of materials over a wide range of wavelengths, irrespective of the intensity of the strength of the light fields. By use of a rotating filter wheel mechanism, it is possible to electronically or optically vary the sensitivity and exposure of the instrument according to the intensity of the measured light field.